Iron(II) catalyzed reductive radical cyclization reactions of bromoacetals in the presence of NaBH4: optimization studies and mechanistic insights
作者:Sara H. Kyne、Christophe Lévêque、Shiwen Zheng、Louis Fensterbank、Anny Jutand、Cyril Ollivier
DOI:10.1016/j.tet.2016.08.039
日期:2016.12
5-Exo-trig radical reductivecyclization reactions of bromoacetals are catalyzed by iron in the presence of the reducing agent NaBH4. Both iron(II) and iron(III) were found to effectively mediate these reactions. As shown by cyclic voltammetry, iron(III) can be reduced to an iron(II) precatalyst before passing through an identical reaction mechanism in which monoelectronic activation of the substrate
Optimizing the ratio of vinyl radical cyclizations through catalysis with diphenyl diselenide
作者:David Crich、Jae-Taeg Hwang、Hui Liu
DOI:10.1016/0040-4039(96)00526-6
日期:1996.4
The 5-exo/6-endo product ratio in the stannane mediated cyclizations of vinyl iodides is very significantly improved by operating in the presence of catalytic PhSeSePh with no loss in overall cyclization yield.
silane promote sequential/cascade free radicalcyclization reactions of dienoate tethered vinyliodides or alkynes. These processes produce [4 + 1] and [4 + 2] annulated products. In contrast, the electrochemical reductions of the vinyliodides afford monocyclic compounds. Both the regiochemical and stereochemical courses of the sequential radicalcyclizations strongly depend on substrate structure.
A photochemically promoted intramolecular cyclization of aryl-, vinyl-, and alkyliodo allenes has been developed. The optimal conditions employed [Ir(ppy)2(dtbbpy)]PF6 (1 mol%) as catalyst affording products with high exo selectivity in moderate to good yields. Chiral substrates showed diastereoselectivity of up to 95/5 favoring trans product.
Stereospecific Synthesis of (+)- and (−)-Cyclooctenone Derivatives Using a Ring Expansion Reaction with Me<sub>3</sub>SiSnBu<sub>3</sub> and CsF
作者:Alice Emi Imai、Yoshihiro Sato、Mayumi Nishida、Miwako Mori
DOI:10.1021/ja983168h
日期:1999.2.1
Novel synthesis of an eight-membered compound by the ringexpansion reaction of a two-carbon unit was developed using the stannyl anion generated from Me3SiSnBu3 and CsF in DMF. cis- and trans-cyclooctenone derivatives were synthesized from cyclohexanone derivatives having vinyl iodide in a tether by treatment with Me3SiSnBu3 and CsF in DMF in a stereospecific manner. The trans-cyclooctenone derivative